Thermal electric assembly attached on an outer surface of a hot section of a gas turbine engine to generate electrical power

ABSTRACT

A gas turbine engine assembly may include a combustion chamber for igniting a fuel and air mixture that generates a core stream flow. The gas turbine engine may also include a hot section cowling for directing the core stream flow through the engine assembly. The hot section cowling may include an inside surface and an outside surface opposite the inside surface. The gas turbine engine assembly may additionally include a plurality of thermoelectric generator (TEG) assemblies that are thermally attached to the outside surface of the hot section cowling. Each TEG assembly may include a multiplicity of thermoelectric generator (TEG) devices that generate an electric current based on a temperature differential across each of the multiplicity of TEG devices. The TEG devices may include different materials that are used in different heat zones along the hot section cowling between the combustion chamber and an exhaust end of the engine.

FIELD

The present disclosure relates to generating electrical power, and moreparticularly to a thermal electric assembly attached on an outer surfaceof a hot section of a gas turbine engine to generate electrical power.

BACKGROUND

Airplanes typically require 28 volts direct current (VDC) forelectrically powering airplane systems that require electrical power.Airplane jet engines or airplane gas turbine engines are required toprovide this electrical power for electrical loads of the airplane, suchas avionics systems, electromechanical systems, and other onboardsystems that require electrical power. Electrical power onboard anairplane is typically supplied by a gear driven generator that isoperatively coupled to a jet engine or gas turbine engine by adriveshaft and gears. The gears and generator remove thrust energy fromthe engine to produce the electrical power. Additionally, hydraulic andbleed air systems of the airplane also remove energy from the enginethat could produce thrust. Accordingly, being able to eliminate thegenerator, drive shaft and gears could improve the efficiency of theengine, eliminate components that are subject to breakdown and requiremaintenance and reduce the weight of the airplane.

SUMMARY

In accordance with an embodiment, a gas turbine engine assembly mayinclude a combustion chamber for igniting a fuel and air mixture thatgenerates a core stream flow. The gas turbine engine may also include ahot section cowling for directing the core stream flow through the gasturbine engine assembly. The hot section cowling may include an insidesurface that contains the core stream flow and an outside surfaceopposite the inside surface. The gas turbine engine assembly may furtherinclude a plurality of thermoelectric generator assemblies thermallyattached to the outside surface of the hot section cowling. Eachthermoelectric generator assembly may include a multiplicity ofthermoelectric generator devices that generate an electric current basedon a temperature differential across each of the multiplicity ofthermoelectric generator devices. The thermoelectric generator devicesmay include different materials that are used in different heat zonesalong the hot section cowling between the combustion chamber and anexhaust end of the hot section cowling or exhaust end of the gas turbineengine.

In accordance with another embodiment, a thermoelectric generationsystem may include a gas turbine engine assembly. The gas turbine engineassembly may include a combustion chamber for igniting a fuel and airmixture that generates a core stream flow. The gas turbine engineassembly may also include a hot section cowling for directing the corestream flow through the gas turbine engine assembly. The hot sectioncowling may include an inside surface that contains the core stream flowand an outside surface opposite the inside surface. The thermoelectricgeneration system may also include a plurality of thermoelectricgenerator assemblies thermally attached to the outside surface of thehot section cowling. Each thermoelectric generator assembly may includea multiplicity of thermoelectric generator devices that generate anelectric current based on a temperature differential across each of theplurality of thermoelectric generator devices. The thermoelectricgenerator devices may include different materials that are used indifferent heat zones along the hot section cowling between thecombustion chamber and an exhaust end of the hot section cowling.

In accordance with a further embodiment, a method for generatingelectrical power may include distributing a plurality of thermoelectricgenerator assemblies along an outside surface of a hot section cowlingof a gas turbine engine. The thermoelectric generator assemblies mayeach include a multiplicity of thermoelectric generator devices. Thethermoelectric generator devices may include different materials used indifferent heat zones along the hot section cowling. The method may alsoinclude capturing waste heat from the hot section cowling of the gasturbine engine by the plurality of thermoelectric generator assembliesand converting the captured waste heat by the plurality ofthermoelectric assemblies into electrical power.

In accordance with another embodiment or any of the previousembodiments, the plurality of thermoelectric generator assemblies may bedistributed along the outside surface of the hot section cowling atpredetermined locations between the combustion chamber and the exhaustend of the hot section cowling to maximize electrical power generation.

In accordance with another embodiment or any of the previousembodiments, the plurality of thermoelectric generator assemblies mayinclude different types of thermoelectric generator devices. Eachdifferent type of thermoelectric generator device may include aparticular group of materials configured to provide a highest efficiencyof thermal energy to electrical energy conversion based on a temperatureof the outside surface of the hot section cowling, during operation ofthe gas turbine engine, where each of the plurality of thermoelectricgenerator assemblies is located between the combustion chamber and theexhaust end of the hot section cowling.

In accordance with another embodiment or any of the previousembodiments, the thermoelectric generator assemblies may includedifferent types of thermoelectric generator devices and are distributedalong the outside surface of the hot section cowling between thecombustion chamber and the exhaust end of the hot section cowling. Thethermoelectric generator devices may be distributed based on anefficiency of each of the different types of thermoelectric generatordevices in converting thermal energy to electrical energy according to atemperature of the outside surface of the hot section cowling at thepredetermined location of each thermoelectric generator assembly.

In accordance with another embodiment or any of the previousembodiments, the gas turbine engine assembly may also include a fan atan inlet to the gas turbine engine assembly that generates a fan streamflow through the gas turbine engine assembly. The gas turbine engineassembly may additionally include a fan nozzle surrounding at least aportion of the hot section cowling. The fan nozzle directs the fanstream flow. The hot section cowling may be continuous from thecombustion chamber to the exhaust end of the hot section cowling. Thefan stream flow passes directly from the fan to the thermoelectricgenerator assemblies without being redirected.

In accordance with another embodiment or any of the previousembodiments, the gas turbine engine assembly may also include a powerbus, a power management system and a power distribution system. Thepower bus provides the electrical power generated by the thermoelectricgenerator assemblies to the power management system and/or powerdistribution system. The power management system may be configured todeliver regulated power to electrically powered components and systemsof a vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of embodiments refers to theaccompanying drawings, which illustrate specific embodiments of thedisclosure. Other embodiments having different structures and operationsdo not depart from the scope of the present disclosure.

FIG. 1 is cross-sectional view of an example of a gas turbine engineincluding a thermoelectric generator assembly system installed on a hotsection of the engine in accordance with an embodiment of the presentdisclosure.

FIG. 2 is cross-sectional view of an example of a gas turbine engineincluding a thermoelectric generator assembly installed on a hot sectionof the engine in accordance with another embodiment of the presentdisclosure.

FIG. 3 is a detailed block schematic diagram of a thermoelectricgenerator assembly installed on an outside surface of a hot section of agas turbine engine in accordance with an embodiment of the presentdisclosure.

FIG. 4 is a graph illustrating an efficiency of different n-typethermoelectric generator materials at different temperatures inaccordance with an embodiment of the present disclosure.

FIG. 5 is a graph illustrating an efficiency of different p-typethermoelectric generator materials at different temperatures inaccordance with an embodiment of the present disclosure.

FIG. 6 is a detailed top view of a thermoelectric generator assembly ofFIG. 1.

FIG. 7 is a schematic diagram of an example of an airplane including aplurality of gas turbine engines and a thermoelectric generator assemblysystem associated with at least one engine for generating electricalpower in accordance with an embodiment of the present disclosure.

FIG. 8 is a flow chart of an example of a method for generatingelectrical power in accordance with an embodiment of the presentdisclosure.

DETAILED DESCRIPTION

The following detailed description of embodiments refers to theaccompanying drawings, which illustrate specific embodiments of thedisclosure. Other embodiments having different structures and operationsdo not depart from the scope of the present disclosure. Like referencenumerals may refer to the same element or component in the differentdrawings.

Certain terminology is used herein for convenience only and is not to betaken as a limitation on the embodiments described. For example, wordssuch as “proximal”, “distal”, “top”, “bottom”, “upper,” “lower,” “left,”“right,” “horizontal,” “vertical,” “upward,” and “downward”, etc.,merely describe the configuration shown in the figures or relativepositions used with reference to the orientation of the figures beingdescribed. Because components of embodiments can be positioned in anumber of different orientations, the directional terminology is usedfor purposes of illustration and is in no way limiting. It is to beunderstood that other embodiments may be utilized and structural orlogical changes may be made without departing from the scope of thepresent invention. The following detailed description, therefore, is notto be taken in a limiting sense, and the scope of the present inventionis defined by the appended claims.

FIG. 1 is cross-sectional view of an example of a gas turbine engineassembly 100 including a thermoelectric generator assembly system 102installed on a hot section 104 of the gas turbine engine assembly 100 inaccordance with an embodiment of the present disclosure. The gas turbineengine assembly 100 may be considered to have at least two sections, acold section 106 and a hot section 104. The cold section 104 may includethat portion of the gas turbine engine assembly 100 before a combustionchamber 108. The hot section 104 may include the combustion chamber 108and that portion of the gas turbine engine assembly 100 aft of thecombustion chamber 108. A gas turbine engine or gas turbine engineassembly 100 may include different configurations. The configuration ofthe exemplary gas turbine engine assembly 100 is an example of atwo-spool, low-bypass turbofan engine. Examples of other configurationsof a gas turbine engine may include a high-bypass turbofan engine and aturbojet engine such as that shown in FIG. 2. The thermoelectricgenerator assembly system 102 described herein may be applicable to anyconfiguration or type of gas turbine engine assembly and anyapplication. Examples of applications of gas turbine engines may includebut is not necessarily limited to propulsion of aircraft and othervehicles, such as watercraft or ships and land craft, and powergeneration. The components and operation of the exemplary gas turbineengine assembly 100 will be described briefly herein for understandingof the disclosure; however, the disclosure is not intended to be limitedby the exemplary configuration described and other configuration may beequally applicable.

The gas turbine engine assembly 100 may include a fan 110 proximate toan inlet 112 or intake formed by a nacelle 114 of the gas turbine engineassembly 100. The nacelle 114 may completely surround a core 115 or bothcold and hot sections 106 and 104 of the gas turbine engine assembly 100as shown in the exemplary gas turbine engine assembly 100 in FIG. 1. Inother embodiments, the nacelle 114 may only surround a portion of thecore 115 of the gas turbine engine assembly 100 or partially extend overthe hot section 104 of the gas turbine engine assembly 100.

An ambient air stream illustrated by arrows 116 may enter the gasturbine engine assembly 100 through the inlet 112 and is rapidlyaccelerated by the fan 110. A portion of the ambient air stream 116accelerated by the fan 110 forms a fan stream flow illustrated by arrows118 that is forced through a bypass air channel 120 or duct to a fannozzle 122 at an aft end or exhaust end 123 of the gas turbine engine100. The bypass air channel 120 may be formed between the nacelle 114 oran outer cowling of the gas turbine engine assembly 100 and an innerwall or inner cowling 124 of the gas turbine engine assembly 100.

Another portion of the ambient air stream 116 accelerated by the fan 110flows through the core 115 of the gas turbine engine assembly 100 whichincludes a low pressure compressor 126 and a high pressure compressor128 in the cold section 106. The low pressure compressor 126 and thehigh pressure compressor 128 further accelerate the ambient air stream116 and generate a high pressure air stream that enters the combustionchamber 108. The low pressure compressor 126 and the high pressurecompressor 128 may each include a series of circular disks or rotors.Each disk or rotor may include a multiplicity of compressor bladesmounted around the circumference of each disk or rotor. The successiverotating disks or rotors in the series progressively accelerate the airstream passing through the low pressure compressor 126 and high pressurecompressor 128 to the combustion chamber 108.

A fuel and air mixture under high pressure is ignited in the combustionchamber 108 and generates a core stream flow illustrated by arrows 130.The highly accelerated core stream flow 130 flows through a highpressure turbine 132 followed by a low pressure turbine 134 forcing thehigh pressure turbine 132 and the low pressure turbine 134 to rotate.The high pressure turbine 132 and the low pressure turbine 134 may eachinclude a series of circular disks or rotors and each disk or rotor mayinclude a multiplicity of turbine blades mounted around thecircumference of each disk or rotor that force the turbines 132 and 134to rotate when impacted by the high velocity core stream flow 130.

The high pressure turbine 132 is operatively coupled to the highpressure compressor 128 by a high pressure shaft 136. Accordingly, thehigh pressure turbine 132 drives the high pressure compressor 128 by thehigh pressure shaft 136. The low pressure turbine 134 is operativelycoupled to the low pressure compressor 126 by a low pressure shaft 138.Thus, the low pressure turbine 134 drives the low pressure compressor126 by the low pressure shaft 138.

The inner wall 124 or cowling in the hot section 104 may be referred toas the hot section cowling 140. The hot section cowling 140 may extendbetween at least proximate an aft or exhaust end of the combustionchamber 108 or high pressure turbine 132 to an exhaust end 142 of thehot section cowling 140 which in some configurations may also be theexhaust end of the gas turbine engine assembly 100. The exhaust end 142of the hot section cowling 140 may also be referred to as a core nozzle.The hot section cowling 140 directs the core stream flow 130 through thegas turbine engine assembly 130. The hot section cowling 140 may includea wall 144. The wall 144 of the hot section cowling 140 may becontinuous from the combustion chamber 108 to the exhaust end 142 of thehot section cowling 140 or core nozzle. The wall 144 of the hot sectioncowling 140 may include an inside surface 146 that contains the corestream flow 130 and an outside surface 148 opposite the inside surface146 or exterior surface of the wall 144.

The thermoelectric generator assembly system 102 may include a pluralityof thermoelectric generator assemblies 150. The plurality ofthermoelectric generator assemblies 150 may be thermally attached to theoutside surface 148 of the hot section cowling 140 or exterior surfaceof the wall 144. The thermoelectric generator assemblies 150 may bethermally attached to the outside surface 148 of the hot section cowling140 at predetermined locations substantially completely around the hotsection cowling 140 or partially around the hot section cowling 140depending upon the amount of electrical power that is desired to begenerated and the quantity of thermoelectric generator assemblies 150that may be required to generate the desired amount of electrical power.Any interstices or gaps between the thermoelectric generator assemblies150 may be filled with a heat resistant material 151 to provide a smoothsurface between and over the thermoelectric generator assemblies 150 forthe fan stream flow 118 to flow without any surface irregularities thatmay disrupt the fan stream flow 118 and cause any possible loss ofefficiency of the gas turbine engine 100. In another embodiment, thethermoelectric generator assemblies 150 may be covered by a surfacematerial 153, as illustrated by the broken line in FIG. 1, that is heatresistant and provides a smooth continuous surface for the fan streamflow 118 to pass over the thermoelectric generator assemblies 150without disruption and loss of engine efficiency. The surface material153 provides sufficient heat transfer or heat flow for efficientgeneration of electrical power by the thermoelectric generatorassemblies 150.

Referring also to FIG. 3, FIG. 3 is a detailed block schematic diagramof an example of a thermoelectric generator assembly 150 installed on anoutside surface 148 of a hot section 104 of a gas turbine engine 100 inaccordance with an embodiment of the present disclosure. The nacelle 114as best shown in FIG. 1 surrounds at least a portion of the hot sectioncowling 140 and directs the fan stream flow to pass over thethermoelectric generator assemblies 150. The hot section cowling 140 maybe continuous from the combustion chamber 108 to the exhaust end 112 orcore nozzle without any plenums or other airstream divertingarrangements. Accordingly, the fan stream flow 118 may pass directlyfrom the fan 110 to the thermoelectric generator assemblies 150 withoutbeing redirected or diverted into any plenums or ducts.

The thermoelectric generator assembly 150 may be bonded to the outsidesurface 148 by a suitable thermally conductive bonding agent 152 oradhesive capable of withstanding the high temperatures on the outsidesurface 148 of the hot section cowling 140. At some locations along thehot section cowling 140 where the temperature of the outside surface 148may exceed limits of the thermoelectric generator assembly 150 and causedamage to the thermoelectric generator assembly 150, a layer 154 ofbuffering material 154 in addition to the bonding agent 152, or thebuffering material 154 in place of the bonding agent 152 or bufferingmaterial 154 added to the bonding agent 152 may be used to protect thethermoelectric generator assembly 150 from damage due to the hightemperature or heat. For example, thermoelectric generator assemblies150 located closer to the combustion chamber 108 (FIG. 1) where thetemperature of the outside surface 148 may be highest, the bufferingmaterial 154 may be required or other material or arrangement to reducethe heat transferred from the outside surface 148 to a hot side 156 ofthe thermoelectric generator assembly 150.

Each thermoelectric generator assembly 150 may include a multiplicity ofthermoelectric generators (TEG) or TEG devices 156 that generate anelectric current based on a temperature differential across each of themultiplicity of TEG devices 156. A TEG or TEG device 156 can generateelectricity when a temperature differential is applied or exists acrossthe device. The TEG device 156 may typically be square or rectangularshaped with an upper and lower end-cap having the same dimension.Typically power generated by TEGs is transmitted via a set of powerwires or terminals 164 or a power bus similar to that described hereinwith reference to FIG. 6. TEG devices 156 are typically thin (e.g., onthe order of a couple of millimeters thick), small (e.g., a couple ofsquare centimeters), flat, and brittle. Accordingly, TEG devices can bedifficult to handle individually, especially for applications in gasturbine engines as described herein and vehicles, such as automobiles,aircraft, and the like, where the TEG devices 156 can be subject toharsh environmental conditions, such as vibration, constant temperaturevariations and other harsh conditions. Because of their size and thefact that each TEG device 156 generates only a small amount of power,many TEG devices 156 are bundled together in order to generate a usefulamount of power. Further, TEG devices 156 generally provide greaterenergy conversion efficiency at high temperature. This can causerelatively large thermal expansion in materials. Because of thermalgradients and different thermal coefficients of expansion associatedwith different materials, thermally induced stresses may result.Efficiency of TEG devices 156 generally increases with greatertemperature differentials, i.e., delta temperature between two oppositesides, typically called the heat source or hot side 158 and heat sink orcold side 160 of the TEG device 156. Also, energy conversion efficiencyis maximized for any installation that channels heat flow through theTEG devices 156 only without any thermal energy leaks through thesurrounding structural material or gaps. Thus, to simplify handling andachieve high performance in converting heat to electricity, multiple TEGdevices 156 can be encased into a module or assembly 150 prior to finalinstallation.

As shown in FIG. 3, the hot side 158 of each TEG device 156 in thethermoelectric generator assembly 150 may be thermally coupled to theoutside surface 148 of hot section cowling 140 by at least the thermallyconductive bonding agent 152, and in areas of the hot section cowling140 that experience temperature extremes that could damage thethermoelectric generator assembly 150, the layer of buffer material 154may be disposed between the hot side 158 of the TEG devices 156 and theouter surface 148. The cold side 160 of each TEG device 156 is exposedto the fan stream flow 118 for creating the temperature differentialacross each TEG device 156 of the thermoelectric generator assembly 150.The flow of heat, as represented by arrow 162, through thethermoelectric generator device 156 due to the difference intemperatures ΔT between the hot side 158 and the cold side 160 causes avoltage ΔV to be generated across electrical terminals 164 of eachthermoelectric generator device 156. The voltage generated by each TEGdevice 156 may be proportion to the temperature differential or heatflow 162 across the TEG device 156 of the thermoelectric generatorassembly 150 or temperature difference between the hot side 158 and coldside 160 of each TEG device 156.

The temperature of a hot section 104 of a gas turbine engine 100 mayvary between about 1200 degrees centigrade (C) and about 600 degrees C.There are available TEG devices that may operate at temperaturesexceeding about 1000 degrees C. As shown in the figures and describedherein, the hot section 104 of the engine 100 is cooled by ambienttemperature or the fan stream flow 118. About a 100 degree C. to about a300 degree C. differential across the TEG device 156 or transitionbetween the hot side 158 and the cold side 160 yields the best resultsor performance in converting heat energy to electrical energy. CurrentTEG devices 156 may convert about 5% to about 8% of the thermal energyto electrical energy.

As previously described, the temperature of the outside surface 148 mayvary along the hot section cowling 140. The thermoelectric generatordevices 156 may include different materials that may be used indifferent heat zones 166 a-166 b (FIG. 1) along the hot section cowling140 between the combustion chamber 108 and the exhaust end 142 of thehot section cowling 140 or core nozzle. For example, a temperature ofthe outside surface 148 of the hot section cowling 140 may be hottest atthe exhaust of the combustion chamber 108 and the temperature of theoutside surface 148 may gradually decrease along the hot section cowling140 toward the exhaust end 142 or core nozzle.

Referring also to FIG. 4 and FIG. 5, FIG. 4 is a graph 400 illustratingan efficiency of different n-type thermoelectric generator materials atdifferent temperatures in accordance with an embodiment of the presentdisclosure. FIG. 5 is a graph 500 illustrating an efficiency ofdifferent p-type thermoelectric generator materials at differenttemperatures in accordance with an embodiment of the present disclosure.The graphs 400 and 500 show ZT for TEG devices composed of differentmaterials over temperatures from 0 degrees C. to 1000 degrees C. ZT is adimensionless figure of merit that corresponds to an ability of a givenmaterial or combination of materials to efficiently produce electricpower. ZT may be defined by the following equation:

${ZT} = \frac{\sigma\; S^{2}T}{\lambda}$Where S is the Seebeck coefficient, λ is the thermal conductivity of thematerial or materials, σ is the electrical conductivity and T is thetemperature. The higher ZT for a particular TEG device composed of acertain material or materials at a particular temperature or temperaturerange, the more efficient the TEG device composed of those materials isat generating electrical power at the particular temperature ortemperature range. Accordingly, thermoelectric generator assemblies 150including TEG devices that have a higher ZT or a higher efficiency ofgenerating electrical power may be used at certain locations along thehot section cowling 140 based on a temperature of the outside surface148 of the hot section cowling 140 during operation of the gas turbineengine.

In accordance with an embodiment, the plurality of thermoelectricgenerator assemblies 150 may be distributed along the outside surface148 of the hot section cowling 140 at predetermined locations betweenthe combustion chamber 108 and the exhaust end 142 of the hot sectioncowling 140 or core nozzle to maximize electrical power generation. Theplurality of thermoelectric generator assemblies 150 may includedifferent types of thermoelectric generator devices 156, each differenttype of thermoelectric generator device 156 may be formed from aparticular material or particular group of materials configured toprovide a highest efficiency of thermal energy to electrical energyconversion based on a temperature of the outside surface 148 of the hotsection cowling 140, during operation of the gas turbine engine 100,where each of the plurality of thermoelectric generator assemblies 150is located between the combustion chamber 108 and the exhaust end 142 ofthe hot section cowling 140 or core nozzle. Therefore, the differenttypes of thermoelectric generator devices 156 may be configured togenerate a predetermined level of electrical power based on atemperature of the outside surface 148 of the hot section cowling 140 atthe predetermined location of the thermoelectric generator assembly 150during operation of the gas turbine engine 100.

In another embodiment, the different types of thermoelectric generatordevices 150 may be distributed along the outside surface 148 of the hotsection cowling 140 between the combustion chamber 108 and the exhaustend 142 of the hot section cowling 140 or core nozzle based on anefficiency of each of the different types of thermoelectric generatordevices 156 in converting thermal energy to electrical energy accordingto a temperature of the outside surface 148 of the hot section cowling140 at the predetermined location of each thermoelectric generatorassembly 150.

FIG. 2 is cross-sectional view of an example of a gas turbine engine 200including a thermoelectric generator assembly 202 installed on a hotsection 204 of the engine 200 in accordance with another embodiment ofthe present disclosure. The exemplary gas turbine engine 200 isconfigured as a turbojet engine. The hot section 204 of the gas turbineengine 200 may include a plurality of combustion chambers 206, a turbine208 aft of the combustion chambers 206 and an exhaust end 210 of the gasturbine engine 200 or exhaust nozzle. The exemplary gas turbine engine200 may include a cold section 212 forward of the a plurality ofcombustion chambers 206.

An ambient air stream represented by arrows 214 may enter an intake 216or air inlet of the gas turbine engine 200. The ambient air stream 214may be accelerated or compressed by a compressor 218 to generate a highspeed compressed air stream flow represented by arrows 220. Thecompressor 218 may be surrounded by a nacelle 222 or cold sectioncowling for directing the compressed air stream flow 220 through thecold section 212. The compressor 218 may include a series of bladedrotors 224. Each bladed rotor 224 may include a multiplicity of bladescircumferentially mounted around a perimeter of a circular disk orrotor. The compressed air stream flow 220 may be directed into thecombustion chambers 206 by the nacelle 222. The compressed air streamflow 220 is mixed with fuel and ignited in the combustion chambers 206to generate a core stream flow 226. The core stream flow 226 is directedfrom the combustion chambers 206 through the turbine 208. A hot sectioncowling 228 encloses the turbine 208 and may extend from at least thecombustion chambers 206 to the exhaust end 210 of the gas turbine engine200. The hot section cowling 228 directs the core stream flow 226through the turbine 208 and out the exhaust end 210 of the gas turbineengine 200 at a high rate of speed for propulsion of an airplane towhich the gas turbine engine 200 may be mounted. The turbine 208 mayinclude a plurality of bladed rotors 230. Each bladed rotor 230 mayinclude a multiplicity of turbine blades circumferentially mountedaround a perimeter of a circular disk or rotor.

A plurality of thermoelectric generator assemblies 202 may be thermallyattached to an outer surface 232 of the hot section cowling 228. Thethermoelectric generator assemblies 202 may be similar to thethermoelectric generator assemblies 150 in FIG. 1. Similar to thethermoelectric generator assemblies 150 shown in FIG. 3, a hot side ofthe thermoelectric generator assemblies 202 may be thermally attached tothe outer surface 232 of the hot section cowling 228 by a suitablethermally conductive bonding agent or adhesive capable of withstandingthe high temperatures on the outer surface 232 of the hot sectioncowling 228. The bonding agent may be the same as bonding agent 152 inFIG. 3. At some locations along the hot section cowling 228 where thetemperature of the outer surface 232 may exceed limits of thethermoelectric generator assembly 202 and cause damage to thethermoelectric generator assembly 202, a layer of buffering material inaddition to the bonding agent, or the buffering material in place of thebonding agent, or buffering material added to the bonding agent 152 maybe used to protect the thermoelectric generator assembly 202 from damagedue to the high temperature or heat. The buffering material may besimilar to the buffering material 154 in FIG. 3.

The temperature of the outer surface 232 may vary along the hot sectioncowling 228. The thermoelectric generator devices 202 may includedifferent materials that may be used in different heat zones 234 a-234 calong the hot section cowling 140 between the combustion chambers 206and the exhaust end 210 of the gas turbine engine 100. For example, atemperature of the outside surface 232 of the hot section cowling 228may be hottest at the exhaust of the combustion chambers 206 and thetemperature of the outside surface 232 may gradually decrease along thehot section cowling 228 toward the exhaust end 210. As previouslydescribed, thermoelectric generator assemblies 202 including differentmaterials may be used at different locations or in different heat zones234 a-234 c to provide the most efficient conversion of thermal energyto electrical energy along the hot section cowling 228.

FIG. 6 is a detailed top view of a thermoelectric generator assembly 150of FIG. 1. As previously described, the thermoelectric generatorassemblies 202 in FIG. 2 may be the same or similar to thethermoelectric generator assemblies 150 in FIG. 1. Each thermoelectricgenerator assembly 150 may include a plurality of thermoelectricgenerator devices 156 similar to those described with reference to FIG.3. The thermoelectric generator devices 156 may be mounted in a frame600 and may be interconnected by electrically wiring 602. The electricalwiring 602 may connect each of the thermoelectric generator devices 156of the thermoelectric generator assembly 150 to a power bus 604. Theelectrical power generated by each of the thermoelectric generatordevices 156 may be provided to the power bus 604 by the electricalwiring 602. Each of the thermoelectric power assemblies 150 in FIG. 1 orthermoelectric power assemblies 202 in FIG. 2 may be connected by thepower bus 604 to a power management system 608. Therefore, theelectrical power generated by each of the thermoelectric powerassemblies 150 or 202 is provided to the power management system 608 bythe power bus 604. The power management system 608 may be a powermanagement system of a vehicle, such as an airplane or other vehicle.The power management system 608 may be configured to convert and/orregulate the electrical power from the thermoelectric power assemblies150 or 202 to electrical power that may be utilized by components orsystems of the vehicle or airplane. Other examples of thermoelectricgenerator assemblies and systems that may be used for thermoelectricpower assemblies 150 or 202 are described in U.S. Pat. No. 9,112,109,entitled “Thermoelectric Generator Assembly and System,” issued Aug. 18,2015, and assigned to the same assignee as the present application andis incorporated herein by reference.

The power management system 608 may be electrically connected to a powerdistribution system 610. The power distribution system 610 may beconfigured to provide regulated electrical power to the electricalsystems and components of the vehicle or airplane. In accordance withsome embodiments, the thermoelectric generator assemblies 150 in FIG. 1or 202 in FIG. 2 may be configured as the only electrical power sourcefor a vehicle. In other embodiments, the thermoelectric generatorassemblies 150 or 202 may be configured as a primary electrical powersource for a vehicle, and in further embodiments, the thermoelectricgenerator assemblies 150 and 202 may be configured as a secondaryelectrical power source for a vehicle.

FIG. 7 is a schematic diagram of an example of an airplane 700 includinga plurality of gas turbine engine assemblies 702 and a thermoelectricgenerator assembly system 704 associated with at least one gas turbineengine assembly 702 for generating electrical power in accordance withan embodiment of the present disclosure. The thermoelectric generatorassembly system 704 may include a plurality of thermoelectric generatorassemblies similar to thermoelectric generator assemblies 150 describedherein. The airplane 700 may also include a fuselage 706 and a wing 708extending from each side of the fuselage 706. In the exemplary airplane700 illustrated in FIG. 7, the gas turbine engine assemblies 702 aremounted under the wings 708. In other embodiments, the gas turbineengine assemblies 702 may be associated with other components of theairplane 700, such as for example, the gas turbine engine assemblies maybe mounted on the fuselage near a tail section 710 of the airplane 700.The tail section 710 of the airplane 700 may include a verticalstabilizer 712 or rudder and a horizontal stabilizer 714 or elevator.

FIG. 8 is a flow chart of an example of a method 800 for generatingelectrical power in accordance with an embodiment of the presentdisclosure. In block 802, a plurality of thermoelectric generatorassemblies may be distributed along an outside surface of a hot sectioncowling of a gas turbine engine. The thermoelectric generator assembliesmay each include a multiplicity of thermoelectric generator devices. Ahot side of each thermoelectric generator assembly may be thermallycoupled to the outer surface of the hot section cowling using athermally conductive bonding agent, adhesive or similar material forthermally attaching the thermoelectric generator assemblies to the hotsection cowling of the engine to capture waste heat from the hot sectionof the engine. A cold side of the thermoelectric generator assembliesmay be exposed to ambient air or a fan stream air flow from a fan of thegas turbine engine. Different types of thermoelectric generatorassemblies that include different types of thermoelectric generatordevices may be used at different locations or distributed amongdifferent heat zones along the hot section cowling based on a surfacetemperature along the hot section cowling to provide a highestefficiency of conversion of thermal energy to electrical energy duringoperation of the gas turbine engine.

In block 804, each of the thermoelectric generator assemblies may beelectrically connected to a power management system and/or to a powerdistribution system by a power bus. A power management system may beprovided to convert and regulate electrical power generated by thethermoelectric generator assemblies to electrical power that is usableby systems and components of a vehicle associated with the gas turbineengine. The electrical power may be distributed to the systems andcomponents of the vehicle by the power distribution system.

In block 806, heat may be transferred from the outside surface of a hotsection of the gas turbine engine to a hot side of the thermoelectricgenerator devices of the thermoelectric generator assemblies duringoperation of the gas turbine engine. The heat may be transferred fromthe outside surface of the hot section to the hot side of thethermoelectric generator devices without diverting flow of hot gasthrough the engine core.

In block 808, cooling air from a fan of the gas turbine engine or a fanairstream or stream flow may flow over exposed cold sides of thethermoelectric generator devices of the thermoelectric generatorassemblies during operation of the gas turbine engine. The cooling airmay flow directly from the fan of the gas turbine engine to the coldside of the thermoelectric devices without diverting the fan streamflow.

In block 810, waste heat captured from the hot section of the gasturbine engine by the thermoelectric generator assemblies may beconverted to electrical power by the thermoelectric generatorassemblies. Electrical power may be generated by a temperaturedifferential between the hot side and a cold side of thermoelectricgenerator devices of each of the thermoelectric generator assemblies asdescribed herein.

In block 812, electrical power generated by the thermoelectric generatorassemblies may be transmitted to a power management system and/or powerdistribution system by a power bus. In block 814, electrical power maybe distributed to the components and systems of a vehicle by the powerdistribution system.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of embodiments ofthe invention. As used herein, the singular forms “a”, “an” and “the”are intended to include the plural forms as well, unless the contextclearly indicates otherwise. It will be further understood that theterms “comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to embodiments of the invention in the form disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of embodiments ofthe invention. The embodiment was chosen and described in order to bestexplain the principles of embodiments of the invention and the practicalapplication, and to enable others of ordinary skill in the art tounderstand embodiments of the invention for various embodiments withvarious modifications as are suited to the particular use contemplated.

Although specific embodiments have been illustrated and describedherein, those of ordinary skill in the art appreciate that anyarrangement which is calculated to achieve the same purpose may besubstituted for the specific embodiments shown and that embodiments ofthe invention have other applications in other environments. Thisapplication is intended to cover any adaptations or variations of thepresent invention. The following claims are in no way intended to limitthe scope of embodiments of the invention to the specific embodimentsdescribed herein.

What is claimed is:
 1. A gas turbine engine assembly, comprising: acombustion chamber for igniting a fuel and air mixture that generates acore stream flow; a hot section cowling for directing the core streamflow through the gas turbine engine assembly, the hot section cowlingcomprising an inside surface that contains the core stream flow and anoutside surface opposite the inside surface; and a plurality ofthermoelectric generator assemblies thermally attached to the outsidesurface of the hot section cowling, each thermoelectric generatorassembly comprising a multiplicity of thermoelectric generator devicesthat generate an electric current based on a temperature differentialacross each of the multiplicity of thermoelectric generator devices,wherein thermoelectric generator devices comprising different n-typethermoelectric generator materials and different p-type thermoelectricgenerator materials are used in different heat zones that have differentoutside surface temperatures along the hot section cowling between thecombustion chamber and an exhaust end of the hot section cowling; and alayer of buffer material disposed between a hot side of thethermoelectric generator devices and the outside surface of the hotsection cowling only in a heat zone closest the combustion chamber toprevent heat damage to the thermoelectric generator devices in the heatzone closest the combustion chamber.
 2. The gas turbine engine assemblyof claim 1, wherein the hot section cowling comprises a wall, the wallof the hot section cowling being continuous from the combustion chamberto the exhaust end of the hot section cowling, and wherein thethermoelectric generator assemblies are thermally attached to anexterior surface of the wall.
 3. The gas turbine engine assembly ofclaim 1, further comprising a fan nozzle surrounding at least a portionof the hot section cowling to direct a fan stream flow, wherein thethermoelectric generator assemblies are exposed to the fan stream flow.4. The gas turbine engine assembly of claim 1, further comprising: a fanat an inlet to the gas turbine engine assembly that generates a fanstream flow through the gas turbine engine assembly; and a fan nozzlesurrounding at least a portion of the hot section cowling, wherein thefan nozzle directs the fan stream flow, and the hot section cowling iscontinuous from the combustion chamber to the exhaust end of the hotsection cowling, the fan stream flow passing directly from the fan tothe thermoelectric generator assemblies without being redirected.
 5. Thegas turbine engine assembly of claim 1, wherein the plurality ofthermoelectric generator assemblies are distributed along the outsidesurface of the hot section cowling at predetermined locations betweenthe combustion chamber and the exhaust end of the hot section cowling tomaximize electrical power generation.
 6. The gas turbine engine assemblyof claim 5, wherein the plurality of thermoelectric generator assembliesincludes different types of thermoelectric generator devices, eachdifferent type of thermoelectric generator device comprising aparticular group of materials configured to provide a highest efficiencyof thermal energy to electrical energy conversion based on a temperatureof the outside surface of the hot section cowling, during operation ofthe gas turbine engine assembly, where each of the plurality ofthermoelectric generator assemblies is located between the combustionchamber and the exhaust end of the hot section cowling.
 7. The gasturbine engine assembly of claim 5, wherein the plurality ofthermoelectric generator assemblies comprises different types ofthermoelectric generator devices, the different types of thermoelectricgenerator devices being configured to generate a predetermined level ofelectrical power based on a temperature of the outside surface of thehot section cowling at a predetermined location of the thermoelectricgenerator assembly during operation of the gas turbine engine.
 8. Thegas turbine engine assembly of claim 5, wherein the thermoelectricgenerator assemblies comprise different types of thermoelectricgenerator devices and are distributed along the outside surface of thehot section cowling between the combustion chamber and the exhaust endof the hot section cowling based on an efficiency of each of thedifferent types of thermoelectric generator devices in convertingthermal energy to electrical energy according to a temperature of theoutside surface of the hot section cowling at a predetermined locationof each thermoelectric generator assembly during operation of the gasturbine engine.
 9. The gas turbine engine assembly of claim 1, furthercomprising: a power bus; and a power management system, wherein thepower bus provides electrical power generated by the thermoelectricgenerator assemblies to the power management system, the powermanagement system being configured to deliver regulated power toelectrically powered components and systems of a vehicle.
 10. The gasturbine engine assembly of claim 1, wherein the gas turbine engineassembly is configured for propulsion of an airplane.
 11. The gasturbine engine assembly of claim 1, wherein the thermoelectric generatorassemblies are configured as a secondary electrical power source for avehicle.
 12. The gas turbine engine assembly of claim 1, wherein thethermoelectric generator assemblies are configured as a primaryelectrical power source for a vehicle.
 13. A thermoelectric generationsystem, comprising: a gas turbine engine assembly, the gas turbineengine assembly comprising: a combustion chamber for igniting a fuel andair mixture that generates a core stream flow; and a hot section cowlingfor directing the core stream flow through the gas turbine engineassembly, the hot section cowling comprising an inside surface thatcontains the core stream flow and an outside surface opposite the insidesurface; a plurality of thermoelectric generator assemblies thermallyattached to the outside surface of the hot section cowling, eachthermoelectric generator assembly comprising a multiplicity ofthermoelectric generator devices that generate an electric current basedon a temperature differential across each of the plurality ofthermoelectric generator devices, the thermoelectric generator devicescomprising different n-type thermoelectric generator materials anddifferent p-type thermoelectric generator materials are used indifferent heat zones that have different outside surface temperaturesalong the hot section cowling between the combustion chamber and anexhaust end of the hot section cowling; and a layer of buffer materialdisposed between a hot side of the thermoelectric generator devices andthe outside surface of the hot section cowling only in a heat zoneclosest the combustion chamber to prevent heat damage to thethermoelectric generator devices in the heat zone closest the combustionchamber.
 14. The thermoelectric generation system of claim 13, furthercomprising a fan at an inlet to the gas turbine engine assembly thatgenerates a fan stream flow through the gas turbine engine assembly; anda fan nozzle surrounding at least a portion of the hot section cowling,the fan nozzle directs the fan stream flow, and the hot section cowlingis continuous from the combustion chamber to the exhaust end of the hotsection cowling, the fan stream flow passing directly from the fan tothe thermoelectric generator assemblies without being redirected. 15.The thermoelectric generation system of claim 13, wherein the pluralityof thermoelectric generator assemblies are distributed along the outsidesurface of the hot section cowling at predetermined locations betweenthe combustion chamber and the exhaust end of the hot section cowling tomaximize electrical power generation.
 16. The gas turbine engineassembly of claim 1, wherein a temperature of the outside surface of thehot section cowling is hottest at an exhaust of the combustion chamberand the temperature of the outside surface gradually decreases along thehot section cowling toward the exhaust end of the hot section cowlingduring operation of the gas turbine engine, wherein different types ofthermoelectric generator devices are distributed along the outsidesurface of the hot section cowling from the combustion chamber to theexhaust end to maximize electrical power generation, each different typeof thermoelectric generator device is formed from a particular materialor group of materials to provide a highest efficiency of thermal energyto electrical energy conversion based on a particular temperate alongthe outside surface of the hot section cowling from the combustionchamber to the exhaust end during operation of the gas turbine engine.17. The gas turbine engine of claim 1, further comprising a heatresistant material disposed within interstices or gaps between thethermoelectric generator assemblies and over the thermoelectricgenerator assemblies for a fan stream flow from a fan of the gas turbineengine without any surface irregularities causing loss of efficiency ofthe gas turbine engine.
 18. The gas turbine engine of claim 1, furthercomprising a surface material covering the plurality of thermoelectricgenerator assemblies, wherein the surface material comprises a smoothcontinuous surface for a fan stream flow from a fan of the gas turbineengine to pass over the thermoelectric generator assemblies withoutdisruption and loss of engine efficiency and the surface materialproviding sufficient heat transfer for efficient generation ofelectrical power by the thermoelectric generator assemblies.
 19. The gasturbine engine of claim 1, wherein the buffering material is added to abonding agent for thermally attaching the thermoelectric generatorassemblies to the outside surface of the hot section cowling.